[Clang importer] Narrow mirrored-import fixes to only consider 'async'.
[Clang importer] Narrow mirrored-import fixes to only consider 'async'.

The previous change was too broad and caused several regressions.

parkera/swift,rudkx/swift,JGiola/swift,gregomni/swift,jmgc/swift,apple/swift,glessard/swift,xwu/swift,hooman/swift,tkremenek/swift,atrick/swift,jmgc/swift,roambotics/swift,rudkx/swift,gregomni/swift,jmgc/swift,ahoppen/swift,benlangmuir/swift,JGiola/swift,roambotics/swift,benlangmuir/swift,apple/swift,hooman/swift,glessard/swift,parkera/swift,xwu/swift,JGiola/swift,ahoppen/swift,atrick/swift,tkremenek/swift,tkremenek/swift,parkera/swift,hooman/swift,benlangmuir/swift,ahoppen/swift,gregomni/swift,JGiola/swift,xwu/swift,gregomni/swift,glessard/swift,rudkx/swift,xwu/swift,glessard/swift,xwu/swift,parkera/swift,hooman/swift,roambotics/swift,xwu/swift,rudkx/swift,roambotics/swift,ahoppen/swift,jmgc/swift,hooman/swift,jmgc/swift,apple/swift,jmgc/swift,roambotics/swift,benlangmuir/swift,tkremenek/swift,apple/swift,xwu/swift,JGiola/swift,roambotics/swift,tkremenek/swift,parkera/swift,hooman/swift,atrick/swift,rudkx/swift,apple/swift,atrick/swift,gregomni/swift,tkremenek/swift,parkera/swift,parkera/swift,ahoppen/swift,parkera/swift,glessard/swift,atrick/swift,apple/swift,JGiola/swift,tkremenek/swift,hooman/swift,ahoppen/swift,atrick/swift,rudkx/swift,jmgc/swift,benlangmuir/swift,benlangmuir/swift,glessard/swift,gregomni/swift